First, you said this is a recession proof industry that is mandated by many companies.
Solution one: connections program. Find out who are the local companies in your metro area that require this type of certification, and begin to call on them to offer some kind of free seminar. Or if your sales team is strong enough, get those local companies to let you do some certification courses for them. You can also establish your company as the leading expert in your field by working some non profits in your area that may need those services as well. A monthly newsletter of some sort may be another good idea. Do whatever you can do to get everyone to take notice that you are there.
Be ready to deal with a lack of funding by non-profits or even for-profits. Here's the point -- if you begin to get noticed by local companies, there's a chance to be recognized by local media. What do you think that can avail you? When used properly, a good PR campaign can increase your visibility quickly with just a good human interest story that somehow ties into what you do in your company. From there it's pretty easy to get into doors simply because everyone saw what good you did recently and they are more open to a conversation with you.
Through an aggressive PR campaign and connections program you can gain the notoriety you need to increase your chances of market share. Use the PR to make those connections. Many companies get the PR then never do anything with it. Use the PR to get businesses' attention. You'll find a much better chance of getting the business when you're known.
This is a first step to a multi-step process you will need to open the satellite offices across the country -- this is usually in the business plan. You may wish to look at it and the marketing plan included to see if there was any blue print laid out early on. They may have figured out most of the work for you already.
Once you have a "footprint" in your metro area, you will want to utilize some kind of referral program to your larger clients that do business elsewhere in the U.S. Why not? If you did them a great service they will trust to hand you over to their colleagues and comrades!
Make sure you utilize as much "free press" as possible so you can keep your budget down and return on investment high. A local marketing solution might also apply here. If you are searchable as a local business service, you may wish to find a way to get marketed locally on and offline.
Start with this and see where it leads you, I bet it will begin to roll on its own to the point you will need only help it along some. Then you can plan your next move and start your building of satellite offices.